Abstract: A method of preserving agricultural products or materials such as hay and silage is disclosed. The method comprises the utilization of a composition for coating the material in order to form a water-repellent protective coating thereon. Preferably the coating includes a preserving agent, having substantial antimicrobial acitivity. Further, in some instances the coating may include an adhesive forming constituent, enabling outer layers of material to become tightly bound in the stack, bale or pile of material being treated. When the latter adhesive compositions are utilized, the treated material tends to retain its physical integrity, against loose portions becoming detached therefrom. Also disclosed are preferred compositions for achieving the methods of treatment, and also preferred methods for preparing certain of the preferred compositions.